1. Field of the Invention
This invention relates to a bisazole-based compound and a Group VIII transition metal complex that is suitable to serve as a dye in a dye-sensitized solar cell, and particularly to a Group VIII transition metal complex containing a bisazole-based ligand.
2. Description of the Related Art
In recent years, solar cells have been developed with the increasing demand for energy. In particular, the dye-sensitized solar cells have shown most promise among solar cells. The dye-sensitized solar cells absorb visible light and near infrared light to excite electrons. The excited electrons are effectively transferred to a conduction band of a semiconductor in the dye-sensitized solar cells to generate a photocurrent. Therefore, the property of a dye used in the dye-sensitized solar cells will affect directly the photoelectric conversion efficiency of the dye-sensitized solar cell. At present, the ruthenium complex is the main target of research for the dye in the solar cell.
U.S. Patent Application Publication No. 2011/0277841 A1 discloses a photosensitizer represented by the following formula (a):RuT1T2T3  (a)
wherein Ru is ruthenium; T1, T2 and T3 represent heterocyclic bidentate ligands, T1 has a chemical formula represented by formula (b), T2 has a chemical formula represented by formulae (b), (c), (d) or (e), and T3 has a chemical formula represented by formulae (c), (d) or (e).

wherein, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, and r18 are independently selected from the group consisting of hydrogen, halogen, aryl group, alkenyl group, C1-C20 alkyl group, cycloalkyl group, alkynyl group, CN, CF3, alkylamino, amino, alkoxy, heteroaryl, halogen substituted aryl group, halogen substituted aromatic group, haloalkyl substituted aryl group, haloalkyl substituted aromatic group and aryl substituted C1-C20 alkyl group.
However, in the case that T1 and T2 of the ruthenium complex have a chemical formula represented by formula (b), the ruthenium complex is a monovalent electropositive complex that is difficult to purify and thus has a low yield.